Isight Camera - Video Fail


I am using iBook with Quicktime Broadcaster to send audio and video across a LAN to another iBook. All was well... but now after a few minutes, the video data rate slows to zero and the video freezes. The audio continues just fine. I thought it was the laptop going to sleep but that was not the issue. Apple tech support could not even begin to figure out what was wrong.

Settings: Unicast to specific IP address. LAN settings for audio and video. SDP file exported and viewed on second computer with quicktime player. Video data rate starts on launch at 500 -600 k/bits per second and slows to 0 for some reason.